In motor vehicles, the exhaust gas generated by an internal combustion engine is frequently re-treated by means of an exhaust gas turbocharger, wherein such an exhaust gas turbocharger for this purpose can be connected to the exhaust line of the internal combustion engine. In addition, the air-fuel ratio of the exhaust gas is controlled in internal combustion engines in that said exhaust gas is sensed with the help of a suitable exhaust gas sensor which is attached in the exhaust tract of the internal combustion engine. Control can take place in the known manner such that the air-fuel ratio sensed by means of the exhaust gas sensor is brought into agreement with a predetermined set value.
Decisive for an optimal function of the exhaust gas sensor is that the latter is attached in a suitable location of the exhaust gas tract so that defective sensor values of the exhaust gas sensor for example due to steam contained in the exhaust gas, which condenses into condensate on the exhaust gas sensor, are avoided. In the case that in the motor vehicle using the internal combustion engine both an exhaust gas turbocharger as well as a catalytic converter unit for cleaning the exhaust gas generated by the internal combustion engine are employed, such an exhaust gas sensor is usually arranged in a region between the exhaust gas turbocharger and the catalytic converter unit. Because of the relatively large thermal mass of the exhaust gas turbocharger, a relatively long period of time is required after a start-up of the internal combustion engine until the exhaust gas tract including exhaust gas turbocharger and (if present) catalytic converter unit in the internal combustion engine have an adequately high temperature so that it is ensured that steam contained in the exhaust gas cannot condense into condensate and lead to undesirable measurement errors for example because of an undesirable wetting of a measurement ceramic of the exhaust gas sensor with condensed steam.
A further disadvantage of conventional exhaust gas sensors, which are directly attached in the intake to the turbine of the exhaust gas turbocharger to avoid the abovementioned problems consists in that it can be damaged because of a thermal overload (thermal shock).
DE 10 2007 021 763 A1 relates to a turbine of a turbocharger, which is arranged on an exhaust gas passage. The turbine comprises an exhaust gas sensor, which is attached downstream and in the vicinity of the turbine of the exhaust gas turbocharger. The structural element of the exhaust gas sensor in this case is arranged on or in the vicinity of an outlet axis of an outlet channel of the turbine of the exhaust gas turbocharger.
DE 10 2009 046 391 A1 describes a method for operating an exhaust gas sensor exposed to the exhaust gas in the exhaust gas tract of an internal combustion engine, according to which exhaust gas is guided to the exhaust gas sensor by means of a capillary. To achieve a robust method, which ensures a highly dynamic measurement of the exhaust gas sensor and does not require any additional structural elements, the exhaust gas flowing to the exhaust gas sensor via the at least one capillary is branched off from the exhaust gas upstream of a stagnation pressure source generating an exhaust gas stagnation pressure.